With the arrival of a rapidly aging society in recent years, senile dementia has become a serious medical and social problem and effective anti-dementia drugs are awaited anxiously. While Alzheimer's disease (AD) has been well studied, its pathogenesis remains unclear. Aricept, the only therapeutic agent for Alzheimer's disease that has been launched in Japan, is based on the inhibitory action on acetylcholinesterase. Although Aricept is very useful for symptomatic treatment, this drug is not a definitive treatment.
One causative substance that induces Alzheimer's disease is thought to be amyloid β protein, which is generated from amyloid precursor protein (APP) through the actions of enzymes called secretases. A compound that has an inhibitory action on these secretases is therefore a promising candidate of a therapeutic agent for Alzheimer's disease. Some compounds that have an inhibitory action on secretases are already known and patent applications for the compounds have been filed (Patent Literatures 1, 2, and 3).